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  Composite rotor for exhaust-gas turbochargers having titanium aluminide wheelsUSPTO Application #: 20070033937Title: Composite rotor for exhaust-gas turbochargers having titanium aluminide wheels Abstract: A rotor for exhaust-gas turbochargers having a turbine wheel (3) made of a metal aluminide, a hollow shaft (2) made of steel or of a nickel-based alloy, and a compressor wheel (1), the compressor wheel (1) having a journal (5), which partially extends into the hollow shaft (2) made of steel or of nickel-based alloy and which forms a positive connection (6) with the same, as well as a method for manufacturing rotors for exhaust-gas turbochargers having a turbine wheel (3), a metal hollow shaft (2), and a compressor wheel (1), including the steps of substance-to-substance bonding of the turbine wheel (3) and of the metal hollow shaft (2), positively connecting the compressor wheel and the metal hollow shaft (2), the positive connection (6) being produced by a journal (5) of the compressor wheel (1) projecting into metal hollow shaft (2), and by the inside of the metal hollow shaft. (end of abstract)
Agent: Davidson, Davidson & Kappel, LLC - New York, NY, US Inventors: Hartmut Baur, Peter Fledersbacher, Michael Scheydecker USPTO Applicaton #: 20070033937 - Class: 060605100 (USPTO) Related Patent Categories: Power Plants, Fluid Motor Means Driven By Waste Heat Or By Exhaust Energy From Internal Combustion Engine, With Supercharging Means For Engine, Supercharging Means Driven By Engine Exhaust Actuated Motor The Patent Description & Claims data below is from USPTO Patent Application 20070033937. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to a rotor for exhaust-gas turbochargers having a turbine wheel made of a metal aluminide, a hollow shaft, and a compressor wheel, as well as to a method for the manufacture thereof with respect to joining the hollow shaft, turbine wheel and compressor wheel. BACKGROUND [0002] The need exists in the automotive industry to replace turbocharger rotors made of steel with those made of light-metal alloys. In this context, the conventional one-piece turbocharger rotors made of steels are replaced with multipiece designs having a highest possible proportion of high-temperature resistant light-metal alloys, since, typically, the quality obtained when manufacturing all-metal aluminide parts is less than satisfactory. It has been established that, for reasons of strength, it is beneficial to continue manufacturing the axial shaft out of steel and to only manufacture the rotor or the compressor wheel out of light metal, respectively metal aluminide. [0003] From the JP-A-2-78734, a turbocharger having a rotor and turbine wheel is known, where the turbine wheel made of .gamma.-titanium aluminide (.gamma.-TiAl) is joined to a steel shaft. Between the turbine wheel and the steel shaft, an intermediate piece made of a nickel-based alloy is provided, which is joined on one side to the turbine wheel in a friction welding process. [0004] From the EP 0 590 197 B1, a method is known for joining a steel shaft having a compressor wheel to a .gamma.-TiAl turbine wheel. In the process, the connection between the steel shaft and the turbine wheel is established by frictionally welding an intermediate piece made of a nickel-based alloy that is permanently joined to the steel shaft. The connection between the steel shaft and the connecting piece is preferably formed in another preliminary friction welding process. [0005] A highly synchronous operation of the exhaust-gas turbocharger rotor is necessary when working with high rotational speeds and high compression ratios. When friction welding is employed for the joining process, the centering and balancing along the longitudinal axis of the rotor is only able to be achieved with difficulty. [0006] Frequently, at least the compressor wheel is screw-coupled to the shaft of the exhaust-gas turbocharger rotor via a bushing. Typically, the screw connection can have a detachable design, which greatly facilitates repairs to the rotor or to the bearings. However, this results in a mechanical weakening of the compressor wheel. In response to elevated temperatures and temperature changes, screw connections of this kind are weakened over the long term. SUMMARY OF THE INVENTION [0007] It is an object of the present invention to devise a rotor for exhaust-gas turbochargers which will feature high-endurance joins between the individual components and a low thermal conductivity between the turbine wheel and the compressor wheel and, respectively, the bearings of the shaft. It is also intended to provide a method suited for manufacturing the same. [0008] The present invention provides a rotor for exhaust-gas turbochargers having a turbine wheel (3) made of a metal aluminide, a hollow shaft (2) made of steel or of a nickel-based alloy, and a compressor wheel (1), also referred to altogether as exhaust-gas turbocharger rotor, wherein the compressor wheel (1) has a journal (5) which partially extends into the hollow shaft (2) made of steel or of nickel-based alloy and which forms a positive connection (6) with the same. [0009] The present invention also provides a method for manufacturing rotors for exhaust-gas turbochargers having a turbine wheel (3), a metal hollow shaft (2), and a compressor wheel (1), including the steps of substance-to-substance bonding of turbine wheel (3) and metal hollow shaft (2), and of positively connecting the compressor wheel and metal hollow shaft (2). BRIEF DESCRIPTION OF THE DRAWINGS [0010] The present invention is described in greater detail below with reference to the schematic drawings, in which: [0011] FIG. 1 shows the exhaust-gas turbocharger rotor in half section along the center axis through steel hollow shaft (2) having compressor wheel (1), turbine wheel (3), journal (5), positive connection (6) and substance-to-substance bond (7); [0012] FIG. 2 is a view of the compressor-wheel side hollow shaft (2) having a slot (8) for a driving element; and [0013] FIG. 3 illustrates the exhaust-gas turbocharger rotor in half section along the center axis through steel hollow shaft (2) having compressor wheel (1), turbine wheel (3), sleeve (4), positive connection (6) and substance-to-substance bond (7). DETAILED DESCRIPTION [0014] It is thus provided in accordance with the present invention that the compressor wheel be joined by a positive connection to the hollow shaft made of steel or nickel-based alloy. This positive connection is produced by way of a journal (5) of compressor wheel (1) which partially extends into the hollow shaft made of steel or of nickel-based alloy. The journal of the turbine wheel and inner wall of the hollow shaft made of steel or of nickel-based alloy are designed in such a way that a permanent substance-to-substance bond is formed. [0015] In comparison to friction-welding technology, this joining technique exhibits the advantage that the hollow shaft and the compressor wheel are able to be joined in a simple manner. On the other hand, special measures are required during friction welding processes to increase the connection surface area, since, by nature, the hollow shaft only has a small contact surface area. [0016] In comparison to a solid shaft, the hollow shaft features the advantage of lower thermal conductivity and of low weight. [0017] The substance-to-substance bond may be produced by employing various measures. In this context, edge forming, round kneading or mechanical interlocking are especially preferred. It is likewise advantageous when the hollow shaft made of steel or of nickel-based alloy is shrunk-fit onto the journal. [0018] It is also a distinguishing feature of the substance-to-substance bond in accordance with the present invention that it is able to be produced with a very precise rotational symmetry with respect to the longitudinal axis of the shaft, respectively of the rotor. This ensures a high-quality synchronous operation, even at the highest rotational speeds. [0019] In one preferred embodiment of the exhaust-gas turbocharger rotor, compressor wheel (1) does not have any recesses or material accumulations for balancing the rotor. It is especially preferred that neither the compressor wheel nor the turbine wheel have such devices for balancing purposes. [0020] The substance-to-substance bond, in particular the mechanical interlocking, may be reinforced by microscopic roughenings or undercuts in the surface of the journal and/or on the inside of the hollow shaft. This eliminates the need for a thread; in the positive connection, preferably neither journal (5) nor hollow shaft (2) made of steel or nickel-based alloy has a thread. Continue reading... Full patent description for Composite rotor for exhaust-gas turbochargers having titanium aluminide wheels Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Composite rotor for exhaust-gas turbochargers having titanium aluminide wheels patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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